ROHS AMS4155 Technical data
http://www.BDTIC.com/AMS
Advanced AMS4155
Monolithic 2A OUTPUT PWM BUCK CONVERTER
Systems
RoHS compliant
FEATURES APPLICATIONS
• Stable with low ESR Output Ceramic Capacitors • Battery Chargers
• Up to 95% Efficiency • Portable (Notebook) Computers
• 2A Continuous Output Current • Industrial power supply
• Wide 4.75V to 20V Operating Input Range • Point of regulation for high performance electronics
• Fixed 480kHz Frequency • Consumer Electronics
• Thermal Shutdown • Audio Power Amplifiers
• Cycle-by-cycle + hiccup Over Current Protection • Distributed Power Systems
• Under Voltage Lockout • Pre-Regulator for Linear Regulators
• Frequency Synchronization Input • LCD TVs and LCD monitors
• Operating Temperature: -40°C to 125°C
• Available in an 8-Pin SO Package
GENERAL DESCRIPTION
The AMS4155 is a monolithic step down switch mode converter with a built in internal power Switch Transistor. It achieves 2A
continuous output current over a wide input supply range with excellent load and line regulation.
Current mode operation provides fast transient response and eases loop stabilization. Fault condition protection includes cycleby-cycle current limiting and thermal shutdown. In shutdown mode the regulator draws 17µA of supply current.
ORDERING INFORMATION
OUTPUT PACKAGE TYPE TEMP. RANGE
VOLTAGE 8 Lead SOIC
Adjustable AMS4155S -25°C to 125°C
TYPICAL APPLICATION
PIN CONNECTIONS
INPUT
470µF/
10µF CER
ON
OFF
EN
SYNC
VIN
8
1
GND
AMS4155
5
BST
COMP
1µF
23
LX
4
F/B
6
7
10nF
5kΩ
Advanced Monolithic Systems, Inc.
B230A
10 µH
30kΩ
10kΩ
OUTPUT
5V/3A
40µF
ceramic
8L SOIC
SO Package (S)
8
EN
7
COMP
6
5FBGNDLX
SYNC
BST
VIN
1
2
3
4
Top View
http://www.BDTIC.com/AMS
PIN DESCRIPTION
Pin Number NAME DESCRIPTION
1 SYNC Synchronization Input. This pin is used to synchronize the internal oscillator frequency to
an external source. Leave SYNC unconnected or connect to GND if unused.
2 BST Bootstrap. This capacitor is needed to drive the power switch above the supply voltage. It
is connected between LX and BST pins to form a floating supply across the power switch
driver. The voltage across Cbst is about 5V and is supplied by the internal Vcc supply
when LX pin voltage is low.
3 VIN Supply Voltage. The AMS4155 operates from a+4.75V to +23V unregulated input. Cin is
needed to prevent large voltage spikes from appearing at the input power supply.
4 LX This connects the inductor to the internal Switch
5 GND Ground Pin connected to PCB ground plane. This pin is also the ground for internal voltage
reference.
6 FB Feedback. A resistor network of two resistors is used to set-up the output voltage connected
between Output to GND. The node between the two resistors is connected to Feedback pin.
AMS4155
7 COMP Compensation. This node is the output of the transconductance error amplifier and the
input to the current comparator. Frequency compensation is done at this node by
connecting a series R-C to ground.
8 ENABLE Enable. A voltage greater than 2.495V at this pin enables device operation.
Advanced Monolithic Systems, Inc.
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